7,000 research outputs found
An efficient Matched Filtering Algorithm for the Detection of Continuous Gravitational Wave Signals
We describe an efficient method of matched filtering over long (greater than
1 day) time baselines starting from Fourier transforms of short durations
(roughly 30 minutes) of the data stream. This method plays a crucial role in
the search algorithm developed by Schutz and Papa for the detection of
continuous gravitational waves from pulsars. Also, we discuss the computational
cost--saving approximations used in this method, and the resultant performance
of the search algorithm.Comment: 4 pages, text only, accepted for publication in the proceedings of
the 3rd Amaldi conference on gravitational wave
Measurement of Knock Characteristics in Spark-ignition Engines
This paper presents a discussion of three potential sources of error in recording engine knocking which are: the natural oscillation of the membrane, the shock process between test contacts, and the danger of burned contacts. Following this discussion, the paper calls attention to various results which make the bouncing-pin indicator appear fundamentally unsuitable for recording knock phenomena
Modulation of a Chirp Gravitational Wave from a Compact Binary due to Gravitational Lensing
A possible wave effect in the gravitational lensing phenomenon is discussed.
We consider the interference of two coherent gravitational waves of slightly
different frequencies from a compact binary, due to the gravitational lensing
by a galaxy halo. This system shows the modulation of the wave amplitude. The
lensing probability of such the phenomenon is of order 10^{-5} for a high-z
source, but it may be advantageous to the observation due to the magnification
of the amplitude.Comment: 3 pages, PRD in pres
Estimating the sensitivity of wide-parameter-space searches for gravitational-wave pulsars
This paper presents an in-depth study of how to estimate the sensitivity of
searches for gravitational-wave pulsars -- rapidly-rotating neutron stars which
emit quasi-sinusoidal gravitational waves. It is particularly concerned with
searches over a wide range of possible source parameters, such as searches over
the entire sky and broad frequency bands. Traditional approaches to estimating
the sensitivity of such searches use either computationally-expensive Monte
Carlo simulations, or analytic methods which sacrifice accuracy by making an
unphysical assumption about the population of sources being searched for. This
paper develops a new, analytic method of estimating search sensitivity which
does not rely upon this unphysical assumption. Unlike previous analytic
methods, the new method accurately predicts the sensitivity obtained using
Monte Carlo simulations, while avoiding their computational expense. The change
in estimated sensitivity due to properties of the search template bank, and the
geographic configuration of the gravitational wave detector network, are also
investigated.Comment: 16 figures, 2 tables, REVTeX 4.1; minor typos corrected from v2,
updated reference
Reducing reflections from mesh refinement interfaces in numerical relativity
Full interpretation of data from gravitational wave observations will require
accurate numerical simulations of source systems, particularly binary black
hole mergers. A leading approach to improving accuracy in numerical relativity
simulations of black hole systems is through fixed or adaptive mesh refinement
techniques. We describe a manifestation of numerical interface truncation error
which appears as slowly converging, artificial reflections from refinement
boundaries in a broad class of mesh refinement implementations, potentially
compromising the effectiveness of mesh refinement techniques for some numerical
relativity applications if left untreated. We elucidate this numerical effect
by presenting a model problem which exhibits the phenomenon, but which is
simple enough that its numerical error can be understood analytically. Our
analysis shows that the effect is caused by variations in finite differencing
error generated across low and high resolution regions, and that its slow
convergence is caused by the presence of dramatic speed differences among
propagation modes typical of 3+1 relativity. Lastly, we resolve the problem,
presenting a class of finite differencing stencil modifications, termed
mesh-adapted differencing (MAD), which eliminate this pathology in both our
model problem and in numerical relativity examples.Comment: 7 page
Non-Gaussian Covariance of the Matter Power Spectrum in the Effective Field Theory of Large Scale Structure
We compute the non-Gaussian contribution to the covariance of the matter
power spectrum at one-loop order in Standard Perturbation Theory (SPT), and
using the framework of the effective field theory (EFT) of large scale
structure (LSS). The complete one-loop contributions are evaluated for the
first time, including the leading EFT corrections that involve seven
independent operators, of which four appear in the power spectrum and
bispectrum. We compare the non-Gaussian part of the one-loop covariance
computed with both SPT and EFT of LSS to two separate simulations. In one
simulation, we find that the one-loop prediction from SPT reproduces the
simulation well to 0.25 h/Mpc, while in the other simulation
we find a substantial improvement of EFT of LSS (with one free parameter) over
SPT, more than doubling the range of where the theory accurately reproduces
the simulation. The disagreement between these two simulations points to
unaccounted for systematics, highlighting the need for improved numerical and
analytic understanding of the covariance.Comment: v2 - 10+9 pages, 6 figures; minor changes + data analysis and
conclusions updated. Version accepted for publication in PR
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